Flexible device and fabrication method of flexible device

ABSTRACT

According to embodiments of the disclosure, a flexible device and a fabrication method thereof are provided. The flexible device has a first area and a second area, and the stiffness of a portion of the first area is greater than the stiffness of the second area. The flexible device may include a flexible substrate and a rigid element. The flexible substrate includes a first surface and a second surface opposite to each other. The second surface has a coarse structure. The surface roughness of the second surface is greater in the first area than in the second area. The rigid element is disposed on the first surface of the flexible substrate and located in the first area. The stiffness of the rigid element is greater than the stiffness of the flexible substrate. A projection area of the coarse structure on the flexible substrate overlaps an area of the rigid element.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority benefit of Taiwan applicationserial no. 103143848, filed on Dec. 16, 2014. The entirety of theabove-mentioned patent application is hereby incorporated by referenceherein and made a part of this specification.

TECHNICAL FIELD

The disclosure relates to a flexible device and a fabrication methodthereof.

BACKGROUND

A flexible device needs a flexible substrate to achieve thecharacteristic of flexibility. However, the flexibility characteristicof the flexible substrate causes the issue that an electronic elementmay not be directly fabricated on the flexible substrate. To fabricatean electronic element on the flexible substrate, the flexible substrateneeds to be adhered on a rigid carrier or machine, so as to provide asuitable support via the carrier or the machine, and thereby theelectronic element may be formed on the flexible substrate. In this way,after the fabrication of the electronic element is complete, theflexible substrate needs to be removed from the rigid carrier ormachine.

A release layer may be used to join the flexible substrate and thecarrier, after the fabrication of the electronic element is complete,the flexible substrate may be removed from the carrier. A suitable peelforce is applied via a mechanical stripping technique to separate theflexible substrate from the carrier. The adhesion provided by therelease layer is not high, and therefore a large peel force does notneed to be applied during mechanical stripping. However, when anelectronic element is fabricated on the flexible substrate, thestiffness of the overall device is not uniform, that is, the stiffnessof some areas is relative greater, and therefore different peel forcesneed to be applied during mechanical stripping. Damage to elements mayoccur in the area to which a greater peel force is applied, which is notgood for production yield.

SUMMARY

According to one embodiment of the disclosure provides a flexibledevice. The flexible device has a first area and a second area, and thestiffness of a portion of the first area is greater than the stiffnessof the second area. The flexible device may include a flexible substrateand a rigid element. The flexible substrate includes a first surface anda second surface opposite to each other, and the second surface of theflexible substrate has a coarse structure in the first area, such thatthe surface roughness of the second surface in the first area is greaterthan the surface roughness of the second surface in the second area. Therigid element is disposed on the first surface of the flexible substrateand located in the first area, wherein the stiffness of the rigidelement is greater than the stiffness of the flexible substrate and aprojection area of the coarse structure on the flexible substrateoverlaps an area of the rigid element.

According to one embodiment of the disclosure provides a fabricationmethod of a flexible device. The fabrication method of the flexibledevice may include temporarily adhering a flexible substrate onto acarrier via a release layer, wherein the flexible substrate has a firstsurface and a second surface, and the second surface is in contact withthe release layer; forming at least one element on the first surface ofthe flexible substrate to form a flexible device, wherein the flexibledevice has a first area and a second area, and the stiffness of aportion of the first area is greater than the stiffness of the secondarea; and irradiating a laser beam from the carrier toward the releaselayer located in the first area, and the irradiation path of the laserbeam falls in the first area.

Several exemplary embodiments accompanied with figures are described indetail below to further describe the disclosure in details.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide further understanding,and are incorporated in and constitute a part of this specification. Thedrawings illustrate exemplary embodiments and, together with thedescription, serve to explain the principles of the disclosure.

FIG. 1A is a top view of a step of a fabrication method of a flexibledevice of the first embodiment of the disclosure.

FIG. 1B is a cross-sectional view along line A-A of FIG. 1A.

FIG. 1C is a cross-sectional view along line B-B of FIG. 1A.

FIG. 2A is a top view of a step of a fabrication method of a flexibledevice of the first embodiment of the disclosure.

FIG. 2B is a cross-sectional view along line A-A of FIG. 2A.

FIG. 2C is a cross-sectional view along line B-B of FIG. 2A.

FIG. 3A is a top view of a step of a fabrication method of a flexibledevice of the first embodiment of the disclosure.

FIG. 3B is a cross-sectional view along line A-A of FIG. 3A.

FIG. 3C is a cross-sectional view along line B-B of FIG. 3A.

FIG. 4A is a top view of a flexible device of the first embodiment ofthe disclosure.

FIG. 4B is a top view of a flexible device of the first embodiment ofthe disclosure.

FIG. 4C is a cross-sectional view along line A-A of FIG. 4A.

FIG. 4D is a cross-sectional view along line B-B of FIG. 4A.

FIG. 5 is a micrograph of a second surface of a flexible substrate ofthe first embodiment of the disclosure.

FIG. 6A is a top view of a step of a fabrication method of a flexibledevice of the second embodiment of the disclosure.

FIG. 6B is a cross-sectional view along line C-C of FIG. 6A.

FIG. 6C is a cross-sectional view along line D-D of FIG. 6A.

FIG. 7A is a top view of a step of a fabrication method of a flexibledevice of the second embodiment of the disclosure.

FIG. 7B is a cross-sectional view along line C-C of FIG. 7A.

FIG. 7C is a cross-sectional view along line D-D of FIG. 7A.

FIG. 7D to FIG. 7F are the irradiation process of a laser beam L alongan irradiation path.

FIG. 8A is a top view of a step of a fabrication method of a flexibledevice of the second embodiment of the disclosure.

FIG. 8B is a cross-sectional view along line C-C of FIG. 8A.

FIG. 8C is a cross-sectional view along line D-D of FIG. 8A.

FIG. 9A is a top view of a flexible device of the second embodiment ofthe disclosure.

FIG. 9B is a top view of a flexible device of the second embodiment ofthe disclosure.

FIG. 10A is a top view of a flexible device of the third embodiment ofthe disclosure.

FIG. 10B is a top view of a flexible device of the third embodiment ofthe disclosure.

FIG. 11A is a top view of a step of a fabrication method of a flexibledevice of the fourth embodiment of the disclosure.

FIG. 11B is a cross-sectional view along line E-E of FIG. 11A.

FIG. 11C is a cross-sectional view along line F-F of FIG. 11A.

FIG. 12A is a top view of a step of a fabrication method of a flexibledevice of the fourth embodiment of the disclosure.

FIG. 12B is a cross-sectional view along line E-E of FIG. 12A.

FIG. 12C is a cross-sectional view along line F-F of FIG. 12A.

FIG. 13A is a top view of a step of a fabrication method of a flexibledevice of the fourth embodiment of the disclosure.

FIG. 13B is a cross-sectional view along line E-E of FIG. 13A.

FIG. 13C is a cross-sectional view along line F-F of FIG. 13A.

FIG. 14 is an embodiment of an irradiation method of a laser beam in thestep of FIG. 2A.

FIG. 15 shows a schematic of a laser irradiation point and aheat-affected zone under an irradiation method of FIG. 14.

FIG. 16 and FIG. 17 are two other embodiments of the irradiation methodof a laser beam in the step of FIG. 2A.

FIG. 18 and FIG. 19 are schematics of different embodiments of the laserirradiation step.

DETAILED DESCRIPTION OF DISCLOSED EMBODIMENTS

FIG. 1A is a top view of a step of a fabrication method of a flexibledevice of the first embodiment of the disclosure, FIG. 1B is across-sectional view along line A-A of FIG. 1A, and FIG. 1C is across-sectional view along line B-B of FIG. 1A. Referring to FIG. 1A toFIG. 1C, a flexible substrate 110 may be temporarily adhered on acarrier 20 via a release layer 10, wherein the flexible substrate 110has a first surface 112 and a second surface 114 opposite to each other,and the second surface 114 is in contact with the release layer 10. Thematerial of the flexible substrate 110 is, for instance, a flexiblematerial such as polyimide (PI), polycarbonate (PC), polyethersulfone(PES), polyacrylate (PA), polynorbornene (PNB), polyethyleneterephthalate (PET), polyetheretherketone (PEEK), polyethylenenaphthalate (PEN), or polyetherimide (PEI). The flexible substrate 110may also have a gas barrier layer. Using PI as example, such type offlexible material may be first coated in liquid state on the carrier 20on which the release layer 10 is formed, and then a curing step isperformed to form the flexible substrate 110, wherein the curing stepmay include a photocuring step, a thermal curing step, or other steps.In other embodiments, the PI material is fabricated into a thin-filmflexible substrate 110, and in the present step, the flexible substrate110 is temporarily adhered on the carrier 20 via the release layer 10.Moreover, since the release layer 10 is used to temporarily adhere theflexible substrate 110 on the carrier 20, the adhesion of the releaselayer 10 does not need to be very strong. In other words, the flexiblesubstrate 110 may be removed from the release layer 10 in a subsequentfabrication step.

As shown in FIG. 1A to FIG. 1C, at least one element 120 is formed onthe first surface 112 of the flexible substrate 110 to constitute aflexible device 100. In the present embodiment, the element 120 includesa rigid element 122 and a functional element 124, wherein the stiffnessof the rigid element 122 is greater than that of the flexible substrate110 and also greater than that of the functional element 124. Therefore,the flexible device 100 may be divided into a first area 102 and asecond area 104, wherein the rigid element 122 is located in the firstarea 102 and the functional element 124 is located in the second area104. Since the rigid element 122 is disposed in the first area 102, thestiffness of the flexible device 100 in the first area 102 is greaterthan the stiffness of the flexible device 100 in the second area 104.

In an embodiment, the rigid element 122 may be, for instance, a drivingchip, and the functional element 124 may be, for instance, an organiclight-emitting element, an inorganic light-emitting element, a sensingelement, a display element, or a combination thereof. In otherembodiments, the rigid element 122 may be an electrode, and thefunctional element 124 may be a battery element. In these embodiments,the rigid element 122 may be electrically connected to the functionalelement 124. Moreover, the rigid element 122 may be a relatively stiffmember in the device, such as a seal or a lateral barrier layer, and therigid element 122 may be disposed in the periphery of the functionalelement 124. The so-called stiffness may substantially becomprehensively determined via, for instance, the thickness and theYoung's modulus of each layer of the element.

In general, by temporarily adhering the flexible substrate 110 on thecarrier 20, desired accuracy and yield may be retained in thefabrication process of the element 120. After the needed elements 120are all fabricated on the flexible substrate 110, the entire flexibledevice 100 needs to be removed from the carrier 20 so as to complete theindependent flexible device 100. The adhesion provided by the releaselayer 10 does not have to be as strong as the average permanent adhesivelayer, and therefore the flexible substrate 110 may be removed from thecarrier 20 by only applying a sufficient peel force. However, when theportion to be peeled has greater stiffness or worse flexibility, thepeel force needed to remove the flexible substrate 110 from the carrier20 is significantly increased. For instance, in an embodiment, when therigid element 122 is a packaged driving chip and the functional element124 is an organic light-emitting element, a release force of about 3.867kg is needed to separate the flexible substrate 110 of the location ofthe rigid element 122 (such as the first area 102 of the presentembodiment) and the carrier 20, and a release force of less than 0.15 kgis needed to separate the other portions (such as the second area 104 ofthe present embodiment) from the carrier 20. Such a release force islikely to cause damage to members on the flexible substrate 110, such aswires fabricated on the flexible substrate 110 or the flexible substrate110 itself which may break as a result, thus causing poor productionyield.

In the present embodiment, before the flexible device 100 and thecarrier 20 are separated, the following steps may be performed. FIG. 2Ais a top view of a step of a fabrication method of a flexible device ofthe first embodiment of the disclosure, FIG. 2B is a cross-sectionalview along line A-A of FIG. 2A, and FIG. 2C is a cross-sectional viewalong line B-B of FIG. 2A. Referring to FIG. 2A to FIG. 2C at the sametime, a laser beam L is for instance irradiated from one side of thecarrier 20 toward the release layer 10 located in the first area 102,and the irradiation path of the laser beam L falls in the first area102. At this point, the release layer 10 irradiated by the laser beam Lis decomposed or modified and converted into a release layer 10A. In thepresent embodiment, the path direction of the laser beam L is, forinstance, from a first side S1 of the flexible substrate 110 toward asecond side S2 of the flexible substrate 110, such that the releaselayer 10A is continuously distributed from the first side S1 to thesecond side S2, and the first side S1 and the second side S2 areopposite sides.

FIG. 3A is a top view of a step of a fabrication method of a flexibledevice of the first embodiment of the disclosure, FIG. 3B is across-sectional view along line A-A of FIG. 3A, and FIG. 3C is across-sectional view along line B-B of FIG. 3A. Referring to FIG. 3A toFIG. 3C at the same time, after the irradiation of the laser beam L isconducted, the flexible device 100 is removed from the carrier 20, suchthat the flexible substrate 110 and the carrier 20 are separated. Here,the step of removing the flexible device 100 may include applying a peelforce at one side of the flexible substrate 110 and peeling the flexiblesubstrate 110 from the carrier 20 along a peeling direction DP.

In the step of FIG. 2A, the adhesion of the release layer 10A is damagedand is reduced when comparing with the release layer 10 without beingirradiated by the laser beam L. Therefore, in the step of FIG. 3A, thepeel force does not need to be significantly increased during theremoval process of the first area 102 in order to separate the flexiblesubstrate 110 of the first area 102 and the carrier 20. In anembodiment, when the rigid element 122 is a packaged driving chip andthe functional element 124 is an organic light-emitting element, and therelease layer 10 is converted to the release layer 10A via theprocessing steps of FIG. 2A to FIG. 2C, about 0.187 kg of peel force isneeded to separate the flexible substrate 110 of the location of therigid element 122 (such as the first area 102 of the present embodiment)and the carrier 20, which is a lot less than the peel force of 3.867 kgneeded before the release layer 10 is processed. Therefore, in thepresent embodiment, members on the flexible substrate 110 are notreadily damaged during the peeling process of the first area 102 fromthe carrier 20, such that the production yield of the flexible device100 may be increased.

FIG. 4A is a top view of a flexible device of the first embodiment ofthe disclosure, FIG. 4B is a top view of a flexible device of the firstembodiment of the disclosure, FIG. 4C is a cross-sectional view alongline A-A of FIG. 4A, and FIG. 4D is a cross-sectional view along lineB-B of FIG. 4A. Referring to FIG. 4A to FIG. 4D at the same time, theflexible device 100 fabricated via the above steps has a first area 102and a second area 104, wherein the stiffness of the first area 102 isgreater than the stiffness of the second area 104. Moreover, theflexible device 100 may include a flexible substrate 110 and an element120 disposed on the flexible substrate 110, wherein the element 120 mayinclude a rigid element 122 and a functional element 124. The flexiblesubstrate 110 includes a first surface 112 and a second surface 114opposite to each other. Moreover, the rigid element 122 is disposed onthe first surface 112 of the flexible substrate 110 and located in thefirst area 102, wherein the stiffness of the rigid element 122 isgreater than the stiffness of the flexible substrate 110 and aprojection area of a coarse structure 114A on the flexible substrate 110overlaps the rigid element 122.

It may be known from FIG. 4B to FIG. 4D that, the second surface 114 ofthe flexible substrate 110 has a coarse structure 114A in the first area102, such that the surface roughness of the second surface 114 in thefirst area 102 is greater than the surface roughness of the secondsurface 114 in the second area 104. The coarse structure 114A may beformed by, for instance, the laser irradiation step of FIG. 2A to FIG.2C. According to the above steps, the laser irradiation step isperformed in the first area 102, and therefore the coarse structure 114Aalso falls in the first area 102. The laser irradiation step isperformed to reduce the adhesion of the release layer 10 where the rigidelement 122 is located, and therefore the irradiation range of the laserbeam overlaps the disposition area of the rigid element 122. Moreover,in the present embodiment, the flexible device 100 further includes afunctional element 124 disposed in the second area 104, and thestiffness of the rigid element 122 is greater than the stiffness of thefunctional element 124, but in other embodiments, the functional element124 may also be optionally omitted. In other words, the flexible device100 may include only the flexible substrate 110 and the rigid element122.

FIG. 5 is a micrograph of a second surface of a flexible substrate ofthe first embodiment of the disclosure. It may be known from FIG. 5that, the second surface 114 has a coarse structure 114A in the firstarea 102, and the second surface 114 appears smooth or translucent inthe second area 104, such that the functional element 124 used as adisplay element is observed. Here, the functional element 124 used as adisplay element is exemplified by an organic light-emitting displaypixel, but is not limited thereto.

It may be known from the first embodiment that, in the laser irradiationstep, the release layer material is decomposed to reduce the adhesion ofthe release layer 10 in the first area 102, thus increasing theproduction yield of the flexible device 100. However, in the case thatthe decomposition of the release layer material generates gas, if thegas generated in the process may not be released or is excessivelyaccumulated, deformation to the first area 102 may readily occur due tothe pressure generated by the gas. Therefore, in the first embodiment,as shown in FIG. 2B, the irradiation path of the laser beam L startsfrom the first side S1 of the flexible substrate 110 and travels towardthe second side S2 of the flexible substrate 110, and the first side S1and the second side S2 are opposite sides. However, the fabricationmethod of the flexible device 100 is not limited thereto.

FIG. 6A is a top view of a step of a fabrication method of a flexibledevice of the second embodiment of the disclosure, FIG. 6B is across-sectional view along line C-C of FIG. 6A, and FIG. 6C is across-sectional view along line D-D of FIG. 6A. In the presentembodiment, the flexible substrate 110 may be temporarily adhered on thecarrier 20 via the release layer 10 according to the steps of FIG. 1A toFIG. 3A, and the element 120 is fabricated on the flexible substrate 110when the flexible substrate 110 is adhered on the carrier 20. Then,referring to FIG. 6A to FIG. 6C, a processing step is performed tofabricate at least one via TH on the flexible substrate 110 to form aflexible substrate 210. The processing step of forming the via TH maybe, for instance, cutting with a round blade, laser cutting, orpunching, but is not limited thereto. Here, the number of the vias TH(via TH1 and via TH2) is two, but this is only exemplary. In otherembodiments, the number of the vias TH may be one or more than two.

In the present embodiment, the rigid element 122 is located between thevia TH1 and the via TH2, and the via TH1 and the via TH2 respectivelydefine two ends of a first area 202. Therefore, the area outside of thefirst area 202 may be regarded as a second area 204. The entire rigidelement 122 falls within the first area 202. Moreover, the via TH1 andthe via TH2 may pass through the flexible substrate 210 to expose therelease layer 10, or pass through the flexible substrate 210 and therelease layer 10 at the same time and expose the carrier 20, and thelatter is exemplified in the following figures.

FIG. 7A is a top view of a step of a fabrication method of a flexibledevice of the second embodiment of the disclosure, FIG. 7B is across-sectional view along line C-C of FIG. 7A, and FIG. 7C is across-sectional view along line D-D of FIG. 7A. The steps represented inFIG. 7A to FIG. 7C include, for instance, irradiating a laser beam Lfrom one side of the carrier 20 toward the release layer 10 located inthe first area 202 to form a release layer 10A in the first area 202. Inthe present embodiment, the irradiation path of the laser beam L startsat the location of the first via TH1 and ends at the location of thesecond via TH2. In other words, the laser beam L moves along a movingdirection DL.

FIG. 7D to FIG. 7F are the irradiation process of a laser beam L alongan irradiation path. It may be known from FIG. 7D to FIG. 7F that, sincethe irradiation path of the laser beam L starts at the location of thefirst via TH1 and travels toward the second via TH2, when the materialof the release layer 10 is decomposed by laser energy, the generated gasmay be dissipated from the first via TH1 (as shown in FIG. 7D and FIG.7E). Moreover, when the irradiation point of the laser beam L is closeto the second via TH2, the generated gas may be dissipated from thesecond via TH2 and the first via TH1. Therefore, accumulation of gasdoes not readily occur at the location of the release layer 10A, suchthat the flexible substrate 210 is not deformed or the flexible device200 is not damaged. In other words, the via TH1 may facilitate thedissipation of gas generated in the fabrication process, thusfacilitating increase in production yield.

FIG. 8A is a top view of a step of a fabrication method of a flexibledevice of the second embodiment of the disclosure, FIG. 8B is across-sectional view along line C-C of FIG. 8A, and FIG. 8C is across-sectional view along line D-D of FIG. 8A. The steps represented byFIG. 8A to FIG. 8C are similar to the steps of FIG. 3A to FIG. 3C, whichinclude the removal of the flexible device 200 from the carrier 20.Specific steps of FIG. 8A to FIG. 8C are as described for FIG. 3A toFIG. 3C. In the first embodiment and the second embodiment, the flexiblesubstrate 110 or 210 is separated from the carrier 20 along the peelingdirection DP, that is, the flexible substrate 110 or 210 is separatedfrom the carrier 20 from the side of the flexible substrate 110 or 210closer to the rigid element 122 toward the opposite side. However, thepeeling direction DP is not limited to the direction represented in thefigure. In other embodiments, the flexible substrate 110 or 210 may alsobe separated from the carrier 20 along a direction opposite to thepeeling direction DP, that is, the flexible substrate 110 or 210 may beseparated from the carrier 20 from the side of the flexible substrate110 or 210 farther from the rigid element 122 toward the opposite side.

FIG. 9A is a top view of a flexible device of the second embodiment ofthe disclosure, and FIG. 9B is a top view of a flexible device of thesecond embodiment of the disclosure. Referring to FIG. 9A and FIG. 9B,the flexible device 200 fabricated according to steps such as FIG. 6A toFIG. 8A may be substantially similar to the flexible device 100 of thefirst embodiment. The flexible device 200 has a first area 202 and asecond area 204, wherein the stiffness of the first area 202 may begreater than the stiffness of the second area 204. Moreover, theflexible device 200 includes a flexible substrate 210 and an element 120disposed on the flexible substrate 210, wherein the element 120 mayinclude a rigid element 122 and a functional element 124. The flexiblesubstrate 210 includes a first surface 212 (shown in FIG. 6B) and asecond surface 214 (shown in FIG. 6B) opposite to each other, and hasvias TH1 and TH2. Moreover, the rigid element 122 is disposed on thefirst surface 212 of the flexible substrate 210 and located in the firstarea 202, wherein the stiffness of the rigid element 122 may be greaterthan the stiffness of the flexible substrate 210. Moreover, the secondsurface 214 of the flexible substrate 210 has a coarse structure 214A inthe first area 202 and a projection area of the coarse structure 214A onthe flexible substrate 210 overlaps the area of the rigid element 122.In other words, the flexible substrate 210 has two vias TH1 and TH2.However, in other embodiments, the flexible substrate 210 may also onlyinclude one via TH, or more than two vias TH.

For instance, FIG. 10A is a top view of a flexible device of the thirdembodiment of the disclosure, and FIG. 10B is a top view of a flexibledevice of the third embodiment of the disclosure. Referring to FIG. 10Aand FIG. 10B, a flexible device 300 may be substantially similar to theflexible device 100 of the first embodiment. The flexible device 300 hasa first area 302 and a second area 304, wherein the stiffness of thefirst area 302 may be greater than the stiffness of the second area 304.Moreover, the flexible device 300 includes a flexible substrate 310 andan element 320 disposed on the flexible substrate 310, wherein theelement 320 may include rigid elements 322A and 322B and a functionalelement 124. The flexible substrate 310 includes a first surface (firstsurface represented in FIG. 10A) and a second surface (second surfacerepresented in FIG. 10B) opposite to each other, and has vias TH1, TH2,and TH3. Moreover, the rigid elements 322A and 322B are disposed on thefirst surface of the flexible substrate 310 and located in the firstarea 302, wherein the stiffness of each of the rigid elements 322A and322B is greater than the stiffness of the flexible substrate 310.Moreover, when the flexible device 300 is fabricated and when therelease layer is, for instance, irradiated via laser, the via TH3 may belocated in the irradiation path of the laser beam or the irradiationpath of the laser beam may pass through the via TH3. As a result, thesecond surface of the flexible substrate 310 has a coarse structure 314Ain the first area 302, and a projection area of the coarse structure314A on the flexible substrate overlaps the rigid elements 322A and322B. In other words, the flexible substrate 310 has three vias TH1,TH2, and TH3, and the flexible substrate 310 has two rigid elements 322Aand 322B. In the three vias TH1, TH2, and TH3, the vias TH1 and TH2define two ends of the first area 302, and the via TH3 is located insidethe first area 302. The rigid element 322A is located between the viaTH1 and the via TH3, and the rigid element 322B is located between thevia TH2 and the via TH3. Moreover, the rigid elements 322A and 322B maybe packaged driving chips, but are not limited thereto.

FIG. 11A is a top view of a step of a fabrication method of a flexibledevice of the fourth embodiment of the disclosure, FIG. 11B is across-sectional view along line E-E of FIG. 11A, and FIG. 11C is across-sectional view along line F-F of FIG. 11A. Referring to FIG. 11Ato FIG. 11C at the same time, the present step includes temporarilyadhering a flexible substrate 410 on a carrier 20 via a release layer10, wherein the area of the release layer 10 is less than the flexiblesubstrate 410 such that the flexible substrate 410 is partially incontact with the carrier 20. Here, a portion 410A of the carrier 20 incontact with the flexible substrate 410 surrounds the release layer 10.The flexible substrate 410 has a first surface 412 and a second surface414, and a portion of the second surface 414 is in contact with therelease layer 10. Moreover, in the present step, at least one element120 is also formed on the first surface 412 of the flexible substrate410. Here, the fabrication method of the flexible substrate 410 is thesame as the fabrication method of the flexible substrate 110 of FIG. 1Ato FIG. 1C, and the fabrication, the type, and the location . . . etc.of the elements 120 are also as described in the first embodiment.

FIG. 12A is a top view of a step of a fabrication method of a flexibledevice of the fourth embodiment of the disclosure, FIG. 12B is across-sectional view along line E-E of FIG. 12A, and FIG. 12C is across-sectional view along line F-F of FIG. 12A. Referring to FIG. 12Ato FIG. 12C, a processing step is performed to cut the flexiblesubstrate 410 along the periphery of the release layer 10 so as to forma circular cut opening V as shown in FIG. 12A, and the cut opening Vexposes the release layer 10, or the cut opening V passes through theflexible substrate 410 and the release layer 10 at the same time andexposes the carrier 20 (FIG. 12B). Here, the flexible substrate 410 iscut into two portions separate from each other, one of the portions is aflexible substrate 410B to be removed and the other portion is theportion 410A in contact with the carrier 20. Moreover, in the presentembodiment, the elements 120 are all fabricated on the flexiblesubstrate 410B to form a flexible device 400.

In the present embodiment, the elements 120 include a rigid element 122and a functional element 124, wherein the stiffness of the rigid element122 may be greater than that of the functional element 124 and alsogreater than that of the flexible substrate 410B. Therefore, theflexible device 400 may have a first area 402 and a second area 404, andthe rigid element 122 is located in the first area 402 such that thestiffness of the first area 402 is greater than that of the second area404.

FIG. 13A is a top view of a step of a fabrication method of a flexibledevice of the fourth embodiment of the disclosure, FIG. 13B is across-sectional view along line E-E of FIG. 13A, and FIG. 13C is across-sectional view along line F-F of FIG. 13A. Referring to FIG. 13Ato FIG. 13C, the flexible device 400 is removed from the carrier 20,such as irradiating from one side of the carrier 20 toward the releaselayer 10 located in the first area 402 via a laser beam L so as to forma release layer 10A in the first area 402. In the present embodiment,since the edge of the flexible substrate 410B is exposed by the cutopening V, the irradiation path of the laser beam L starts from thefirst side S1 of the flexible substrate 410 and travels toward thesecond side S2 of the flexible substrate 410, and the first side S1 andthe second side S2 are opposite sides. Moreover, the peeling directionof the removal of the flexible device 400 from the carrier 20 may be thesame as FIG. 13C in that peel force is applied from a third side S3 ofthe flexible substrate 410B toward a fourth side S4 of the flexiblesubstrate 410B, or the peel force is applied from the fourth side S4 ofthe flexible substrate 410B toward the third side S3 of the flexiblesubstrate 410B. Here, the third side S3 is farther from the rigidelement 122 and the fourth side S4 is closer to the rigid element 122.Therefore, when peeling the flexible device 400 from the carrier 20 viathe method of FIG. 13C, the peeling step and the laser irradiation stepmay be performed at the same time, but the disclosure is not limitedthereto. In other embodiments, the laser irradiation step may be beforethe peeling step. Moreover, similar to the above embodiments, in thelaser irradiation step, a coarse structure 414A is formed on the secondsurface 414 of the flexible substrate 410B, and the laser irradiationstep is only performed in the first area 402, and therefore the coarsestructure 414A is also only located in the first area 402.

In the above embodiments, the irradiation of the laser beam maydecompose or modify the release layer material and thereby reduce theadhesion of the release layer in the irradiated area. However, heataccumulation phenomenon may occur to the periphery of the areairradiated by the laser beam. The heat accumulation phenomenon may causethe adhesion of the release layer material to increase and is not goodfor the peeling step. Therefore, the irradiation method of a laser beammay be adjusted accordingly.

The irradiation method of a laser beam is described in the followingbased on the step of FIG. 2A.

FIG. 14 is an embodiment of an irradiation method of a laser beam in thestep of FIG. 2A. Referring to FIG. 14A, the members in the presentfigure are all as described for FIG. 2A and are not repeated herein.When the laser irradiation step is performed via a dot laser beam LB,the irradiation point LB of the laser beam travels, for instance, alonga trajectory P1. Moreover, the area of each irradiation point LB of thelaser beam partially overlaps the area of the previous irradiation pointLB. The irradiation points LB of the laser beam cover the entire firstarea 102, and therefore the coarse structure generated based on laserirradiation in the above embodiments also covers the entire first area102.

FIG. 15 shows a schematic of a laser irradiation point and aheat-affected zone under an irradiation method of FIG. 14. Referring toboth FIG. 14 and FIG. 15, the irradiation point LB of each laser beamcorresponds to a heat-affected zone HB, and the area of theheat-affected zone HB is greater than the area of the irradiation pointLB. When two overlapping irradiation points LB, such as irradiationpoints LB1 and LB2 are irradiated in a consecutive manner, theheat-affecting effect of the corresponding heat-affected zones HB1 andHB2 may be increased. Therefore, the overlapping portion of theheat-affected zones HB1 and HB2, such as a heat-affected zone HBS, hasthe most heat-affecting effect. In other words, the adhesion of therelease layer material in the heat-affected zone HBS may be moreincreased. Therefore, when the flexible substrate 110 is to be peeledfrom the carrier 20 along the peeling direction DP, the heat-affectedzone HBS is preferably not densely arranged in a direction Rperpendicular to the peeling direction DP, which causes difficultpeeling. In the present embodiment, since the irradiation point LB ofthe laser beam travels along the trajectory P1, the heat-affected zoneHBS is arranged to be substantially parallel to the peeling directionDP, so as to prevent difficulty in peeling.

FIG. 16 and FIG. 17 are two other embodiments of the irradiation methodof a laser beam in the step of FIG. 2A. In FIG. 16, the irradiationpoint LB of a laser beam travels, for instance, along a trajectory P2,and overlapping does not occur between irradiation points LB, whereinthe trajectory P2 is substantially formed by the connection of aplurality of V-type paths. At this point, the irradiation points LB aredistributed in a partial area of the first area 102, and therefore thecoarse structure generated based on laser irradiation in the aboveembodiments is also distributed in a partial area of the first area 102.Moreover, in FIG. 17, overlapping may also not occur between theirradiation points LB, and the irradiation points LB of the laser beamtravel along a trajectory P3, wherein the trajectory P3 may be similarto the trajectory P1 of FIG. 14 in that both are winding trajectories,but the trajectory P3 is more sparsely distributed and the trajectory P1is more densely distributed.

In addition to controlling the travel trajectory of the irradiationpoints, a negative effect to the peeling step by a heat-affected zonemay also be reduced via the incident angle of the laser beam. Forinstance, FIG. 18 and FIG. 19 are schematics of different embodiments ofthe laser irradiation step. In FIG. 18 and FIG. 19, the irradiationdirection of the laser beam L may be not perpendicular to the flexiblesubstrate 110, and irradiation may be performed in the irradiationdirection of an angle of □1, □2, or □3. Therefore, the release layer 10Airradiated by laser may have a trapezoidal (FIG. 18) or approximateparallelogram (FIG. 19) cross-sectional profile. By controlling theirradiation location of the laser beam, the heat-affected zone HB may belocated at the edge of the rigid element 122 and inclined at an angle.In this way, the flexible substrate 110 is separated from the carrier 20along separating interfaces Z1 and Z2 when removed from the carrier 20.In other words, in the area not irradiated by the laser beam, theseparating interface Z1 is located between the release layer 10 and theflexible substrate 110, and in the area irradiated by the laser, since aportion of the material of the release layer 10A is decomposed, theseparating interface Z2 is located between the release layer 10A and thecarrier 20. In FIG. 18, the orthographic projections of the separatinginterface Z1 and the separating interface Z2 on the flexible substrate110 are overlapped with each other and continuously cover the entirearea of the flexible substrate 110, and therefore the flexible substrate110 may be readily peeled from the carrier 20. The embodiment of FIG. 19is no different.

In the fabrication method of a flexible electronic device of theembodiments of the disclosure, before the flexible device is removedfrom the carrier, a laser irradiation step . . . etc. is first performedon the area having greater stiffness to reduce the peel force needed forthis area. Therefore, the fabrication method of a flexible electronicdevice has a desirable yield. Moreover, the embodiments of thedisclosure do not readily damage members on the flexible device, andtherefore the flexible device of the embodiments of the disclosure has adesirable quality.

It will be clear that various modifications and variations may be madeto the disclosed methods and materials. It is intended that thespecification and examples be considered as exemplary only, with a truescope of the disclosure being indicated by the following claims andtheir equivalents.

What is claimed is:
 1. A flexible device having a first area and asecond area, wherein a stiffness of a portion of the first area isgreater than a stiffness of the second area, the flexible devicecomprising: a flexible substrate comprising a first surface and a secondsurface opposite to each other, and the second surface of the flexiblesubstrate has a coarse structure in the first area, such that a surfaceroughness of the second surface in the first area is greater than asurface roughness of the second surface in the second area; and a rigidelement disposed on the first surface of the flexible substrate andlocated in the first area, wherein a stiffness of the rigid element isgreater than a stiffness of the flexible substrate and a projection areaof the coarse structure on the flexible substrate overlaps an area ofthe rigid element.
 2. The flexible device of claim 1, further comprisinga functional element disposed on the first surface of the flexiblesubstrate and located in the second area, wherein the stiffness of therigid element is greater than a stiffness of the functional element. 3.The flexible device of claim 2, wherein the functional element comprisesan organic light-emitting element, an inorganic light-emitting element,a sensing element, a display element, a battery element, or acombination thereof.
 4. The flexible device of claim 2, wherein therigid element is electrically connected to the functional element. 5.The flexible device of claim 2, wherein the rigid element is located ina periphery of the functional element.
 6. The flexible device of claim1, wherein the flexible substrate has at least one via defining one endof the first area.
 7. The flexible device of claim 1, wherein theflexible substrate has at least one via located in the first area. 8.The flexible device of claim 1, wherein the first area is extended froma first side of the flexible substrate to a second side of the flexiblesubstrate, and the first side and the second side are opposite sides. 9.The flexible device of claim 1, wherein the coarse structure covers thefirst area.
 10. The flexible device of claim 1, wherein the coarsestructure is distributed along a trajectory in the first area anddistributed in a partial area of the first area.
 11. A fabricationmethod of a flexible device, comprising: temporarily adhering a flexiblesubstrate on a carrier via a release layer, wherein the flexiblesubstrate has a first surface and a second surface, and the secondsurface is in contact with the release layer; forming at least oneelement on the first surface of the flexible substrate to form aflexible device, wherein the flexible device has a first area and asecond area, and a stiffness of a portion of the first area is greaterthan a stiffness of the second area; and irradiating a laser beam fromthe carrier toward the release layer located in the first area, and anirradiation path of the laser beam falls in the first area.
 12. Themethod of claim 11, further comprising, after the irradiation of thelaser beam is complete, removing the flexible device from the carrier,such that the flexible substrate and the carrier are separated.
 13. Themethod of claim 11, further comprising, before the irradiation of thelaser beam is performed, performing a processing step to form at leastone via on the flexible substrate to expose the release layer or thecarrier.
 14. The method of claim 13, wherein the at least one viacomprises a first via and a second via respectively defining twoopposite ends of the first area, and the irradiation path of the laserbeam starts from a location of the first via and ends at a location ofthe second via.
 15. The method of claim 11, wherein the irradiation pathof the laser beam starts from a first side of the flexible substrate andtravels toward a second side of the flexible substrate, and the firstside and the second side are opposite sides.
 16. The method of claim 11,wherein an irradiation area of the laser beam covers the first area. 17.The method of claim 11, wherein an irradiation area of the laser beamaccounts for a portion of the first area.
 18. The method of claim 11,wherein an irradiation direction of the laser beam is not perpendicularto the flexible substrate.
 19. The method of claim 11, wherein an areaof the release layer is less than the flexible substrate and a portionof the flexible substrate is in contact with the carrier.
 20. The methodof claim 19, further comprising, before the irradiation of the laserbeam is performed, performing a processing step on the flexiblesubstrate to form a cut opening, and the cut opening surrounds therelease layer and exposes the release layer or the carrier.